Remove the Flags type from Config API (#769)

* Remove the `Flags` type from `Config` API

This commit removes the final foreign type from the `Config` API in the
`wasmtime` crate. The cranelift `Flags` type is now expanded into
various options on the `Config` structure itself, all prefixed with
`cranelift_` since they're only relevant to the Cranelift backend. The
various changes here were:

* The `avoid_div_traps` feature is enabled by default since it seemed
  that was done anywhere anyway.
* Enabling the wasm SIMD feature enables the requisite features in
  Cranelift as well.
* A method for enabling the debug verifier has been added.
* A method for configuring the Cranelift optimization level, as well as
  a corresponding enumeration, has been added.

* Assert that `Config` is both `Send` and `Sync`

Cargo.lock

@@ -1991,7 +1991,6 @@ dependencies = [
  "wasmtime-interface-types",
  "wasmtime-jit",
  "wasmtime-obj",
- "wasmtime-runtime",
  "wasmtime-wasi",
  "wasmtime-wasi-c",
  "wasmtime-wast",

Cargo.toml

@@ -19,7 +19,6 @@ wasmtime = { path = "crates/api" }
 wasmtime-debug = { path = "crates/debug" }
 wasmtime-environ = { path = "crates/environ" }
 wasmtime-interface-types = { path = "crates/interface-types" }
-wasmtime-runtime = { path = "crates/runtime" }
 wasmtime-jit = { path = "crates/jit" }
 wasmtime-obj = { path = "crates/obj" }
 wasmtime-wast = { path = "crates/wast" }

crates/api/src/context.rs

@@ -2,6 +2,7 @@ use crate::Config;
 use std::cell::{RefCell, RefMut};
 use std::hash::{Hash, Hasher};
 use std::rc::Rc;
+use wasmtime_environ::settings;
 use wasmtime_jit::{native, Compiler, Features};
 
 #[derive(Clone)]
@@ -13,7 +14,7 @@ pub struct Context {
 
 impl Context {
     pub fn new(config: &Config) -> Context {
-        let isa = native::builder().finish(config.flags.clone());
+        let isa = native::builder().finish(settings::Flags::new(config.flags.clone()));
         Context::new_with_compiler(config, Compiler::new(isa, config.strategy))
     }
 

crates/api/src/lib.rs

@@ -27,7 +27,7 @@ pub use crate::externals::*;
 pub use crate::instance::Instance;
 pub use crate::module::Module;
 pub use crate::r#ref::{AnyRef, HostInfo, HostRef};
-pub use crate::runtime::{Config, Engine, Store, Strategy};
+pub use crate::runtime::{Config, Engine, OptLevel, Store, Strategy};
 pub use crate::trap::{FrameInfo, Trap, TrapInfo};
 pub use crate::types::*;
 pub use crate::values::*;

crates/api/src/runtime.rs

@@ -4,18 +4,16 @@ use std::cell::RefCell;
 use std::collections::HashMap;
 use std::rc::Rc;
 use std::sync::Arc;
-use wasmtime_environ::{ir, settings};
+use wasmtime_environ::{
+    ir,
+    settings::{self, Configurable},
+};
 use wasmtime_jit::{CompilationStrategy, Features};
 
 // Runtime Environment
 
 // Configuration
 
-fn default_flags() -> settings::Flags {
-    let flag_builder = settings::builder();
-    settings::Flags::new(flag_builder)
-}
-
 /// Global configuration options used to create an [`Engine`] and customize its
 /// behavior.
 ///
@@ -23,7 +21,7 @@ fn default_flags() -> settings::Flags {
 /// [`Engine::new()`]
 #[derive(Clone)]
 pub struct Config {
-    pub(crate) flags: settings::Flags,
+    pub(crate) flags: settings::Builder,
     pub(crate) features: Features,
     pub(crate) debug_info: bool,
     pub(crate) strategy: CompilationStrategy,
@@ -33,10 +31,18 @@ impl Config {
     /// Creates a new configuration object with the default configuration
     /// specified.
     pub fn new() -> Config {
+        let mut flags = settings::builder();
+
+        // There are two possible traps for division, and this way
+        // we get the proper one if code traps.
+        flags
+            .enable("avoid_div_traps")
+            .expect("should be valid flag");
+
         Config {
             debug_info: false,
             features: Default::default(),
-            flags: default_flags(),
+            flags,
             strategy: CompilationStrategy::Auto,
         }
     }
@@ -50,16 +56,6 @@ impl Config {
         self
     }
 
-    /// Configures various flags for compilation such as optimization level and
-    /// such.
-    ///
-    /// For more information on defaults and configuration options, see the
-    /// documentation for [`Flags`](settings::Flags)
-    pub fn flags(&mut self, flags: settings::Flags) -> &mut Self {
-        self.flags = flags;
-        self
-    }
-
     /// Configures whether the WebAssembly threads proposal will be enabled for
     /// compilation.
     ///
@@ -116,6 +112,10 @@ impl Config {
     /// [proposal]: https://github.com/webassembly/simd
     pub fn wasm_simd(&mut self, enable: bool) -> &mut Self {
         self.features.simd = enable;
+        let val = if enable { "true" } else { "false" };
+        self.flags
+            .set("enable_simd", val)
+            .expect("should be valid flag");
         self
     }
 
@@ -165,6 +165,8 @@ impl Config {
     /// modules, and for more documentation consult the [`Strategy`] enumeration
     /// and its documentation.
     ///
+    /// The default value for this is `Strategy::Auto`.
+    ///
     /// # Errors
     ///
     /// Some compilation strategies require compile-time options of `wasmtime`
@@ -183,6 +185,41 @@ impl Config {
         };
         Ok(self)
     }
+
+    /// Configures whether the debug verifier of Cranelift is enabled or not.
+    ///
+    /// When Cranelift is used as a code generation backend this will configure
+    /// it to have the `enable_verifier` flag which will enable a number of debug
+    /// checks inside of Cranelift. This is largely only useful for the
+    /// developers of wasmtime itself.
+    ///
+    /// The default value for this is `false`
+    pub fn cranelift_debug_verifier(&mut self, enable: bool) -> &mut Self {
+        let val = if enable { "true" } else { "false" };
+        self.flags
+            .set("enable_verifier", val)
+            .expect("should be valid flag");
+        self
+    }
+
+    /// Configures the Cranelift code generator optimization level.
+    ///
+    /// When the Cranelift code generator is used you can configure the
+    /// optimization level used for generated code in a few various ways. For
+    /// more information see the documentation of [`OptLevel`].
+    ///
+    /// The default value for this is `OptLevel::None`.
+    pub fn cranelift_opt_level(&mut self, level: OptLevel) -> &mut Self {
+        let val = match level {
+            OptLevel::None => "none",
+            OptLevel::Speed => "speed",
+            OptLevel::SpeedAndSize => "speed_and_size",
+        };
+        self.flags
+            .set("opt_level", val)
+            .expect("should be valid flag");
+        self
+    }
 }
 
 impl Default for Config {
@@ -215,6 +252,20 @@ pub enum Strategy {
     Lightbeam,
 }
 
+/// Possible optimization levels for the Cranelift codegen backend.
+#[non_exhaustive]
+#[derive(Clone, Debug)]
+pub enum OptLevel {
+    /// No optimizations performed, minimizes compilation time by disabling most
+    /// optimizations.
+    None,
+    /// Generates the fastest possible code, but may take longer.
+    Speed,
+    /// Similar to `speed`, but also performs transformations aimed at reducing
+    /// code size.
+    SpeedAndSize,
+}
+
 // Engine
 
 /// An `Engine` which is a global context for compilation and management of wasm
@@ -313,4 +364,5 @@ impl Store {
 fn _assert_send_sync() {
     fn _assert<T: Send + Sync>() {}
     _assert::<Engine>();
+    _assert::<Config>();
 }

crates/environ/src/data_structures.rs

@@ -9,7 +9,7 @@ pub mod ir {
 }
 
 pub mod settings {
-    pub use cranelift_codegen::settings::{builder, Configurable, Flags};
+    pub use cranelift_codegen::settings::{builder, Builder, Configurable, Flags};
 }
 
 pub mod isa {

crates/test-programs/tests/wasm_tests/runtime.rs

@@ -1,21 +1,10 @@
 use anyhow::{bail, Context};
 use std::fs::File;
 use std::path::Path;
-use wasmtime::{Config, Engine, HostRef, Instance, Module, Store};
-use wasmtime_environ::settings::{self, Configurable};
+use wasmtime::{Engine, HostRef, Instance, Module, Store};
 
 pub fn instantiate(data: &[u8], bin_name: &str, workspace: Option<&Path>) -> anyhow::Result<()> {
-    // Prepare runtime
-    let mut flag_builder = settings::builder();
-
-    // Enable proper trap for division
-    flag_builder
-        .enable("avoid_div_traps")
-        .context("error while enabling proper division trap")?;
-
-    let mut config = Config::new();
-    config.flags(settings::Flags::new(flag_builder));
-    let engine = Engine::new(&config);
+    let engine = Engine::default();
     let store = HostRef::new(Store::new(&engine));
 
     let global_exports = store.borrow().global_exports().clone();

src/bin/wasmtime.rs

@@ -36,7 +36,6 @@ use wasi_common::preopen_dir;
 use wasmtime::{Config, Engine, HostRef, Instance, Module, Store};
 use wasmtime_cli::pick_compilation_strategy;
 use wasmtime_environ::{cache_create_new_config, cache_init};
-use wasmtime_environ::{settings, settings::Configurable};
 use wasmtime_interface_types::ModuleData;
 use wasmtime_wasi::create_wasi_instance;
 use wasmtime_wasi::old::snapshot_0::create_wasi_instance as create_wasi_instance_snapshot_0;
@@ -231,29 +230,21 @@ fn main() -> Result<()> {
     }
 
     let mut config = Config::new();
-    let mut flag_builder = settings::builder();
-
-    // There are two possible traps for division, and this way
-    // we get the proper one if code traps.
-    flag_builder.enable("avoid_div_traps")?;
 
     // Enable/disable producing of debug info.
     config.debug_info(args.flag_g);
 
     // Enable verifier passes in debug mode.
-    if cfg!(debug_assertions) {
-        flag_builder.enable("enable_verifier")?;
-    }
+    config.cranelift_debug_verifier(cfg!(debug_assertions));
 
     // Enable SIMD if requested
     if args.flag_enable_simd {
-        flag_builder.enable("enable_simd")?;
         config.wasm_simd(true);
     }
 
     // Enable optimization if requested.
     if args.flag_optimize {
-        flag_builder.set("opt_level", "speed")?;
+        config.cranelift_opt_level(wasmtime::OptLevel::Speed);
     }
 
     // Decide how to compile.
@@ -261,7 +252,6 @@ fn main() -> Result<()> {
         args.flag_cranelift,
         args.flag_lightbeam,
     )?)?;
-    config.flags(settings::Flags::new(flag_builder));
     let engine = Engine::new(&config);
     let store = HostRef::new(Store::new(&engine));
 

src/bin/wast.rs

@@ -29,8 +29,6 @@ use std::path::Path;
 use std::process;
 use wasmtime::{Config, Engine, HostRef, Store};
 use wasmtime_cli::pick_compilation_strategy;
-use wasmtime_environ::settings;
-use wasmtime_environ::settings::Configurable;
 use wasmtime_environ::{cache_create_new_config, cache_init};
 use wasmtime_wast::WastContext;
 
@@ -118,25 +116,16 @@ fn main() -> Result<()> {
     }
 
     let mut cfg = Config::new();
-    let mut flag_builder = settings::builder();
-
-    // There are two possible traps for division, and this way
-    // we get the proper one if code traps.
-    flag_builder.enable("avoid_div_traps").unwrap();
-
     // Enable verifier passes in debug mode.
-    if cfg!(debug_assertions) {
-        flag_builder.enable("enable_verifier").unwrap();
-    }
+    cfg.cranelift_debug_verifier(cfg!(debug_assertions));
 
     // Enable optimization if requested.
     if args.flag_optimize {
-        flag_builder.set("opt_level", "speed").unwrap();
+        cfg.cranelift_opt_level(wasmtime::OptLevel::Speed);
     }
 
     // Enable SIMD if requested
     if args.flag_enable_simd {
-        flag_builder.enable("enable_simd").unwrap();
         cfg.wasm_simd(true);
     }
 
@@ -144,8 +133,7 @@ fn main() -> Result<()> {
     cfg.strategy(pick_compilation_strategy(
         args.flag_cranelift,
         args.flag_lightbeam,
-    )?)?
-    .flags(settings::Flags::new(flag_builder));
+    )?)?;
     let store = HostRef::new(Store::new(&Engine::new(&cfg)));
     let mut wast_context = WastContext::new(store);
 

tests/wast_testsuites.rs

@@ -1,7 +1,5 @@
 use std::path::Path;
 use wasmtime::{Config, Engine, HostRef, Store, Strategy};
-use wasmtime_environ::settings;
-use wasmtime_environ::settings::Configurable;
 use wasmtime_wast::WastContext;
 
 include!(concat!(env!("OUT_DIR"), "/wast_testsuite_tests.rs"));
@@ -12,16 +10,11 @@ include!(concat!(env!("OUT_DIR"), "/wast_testsuite_tests.rs"));
 fn run_wast(wast: &str, strategy: Strategy) -> anyhow::Result<()> {
     let wast = Path::new(wast);
 
-    let mut flag_builder = settings::builder();
-    flag_builder.enable("enable_verifier").unwrap();
-    flag_builder.enable("avoid_div_traps").unwrap();
-    flag_builder.enable("enable_simd").unwrap();
-
     let mut cfg = Config::new();
     cfg.wasm_simd(wast.iter().any(|s| s == "simd"))
         .wasm_multi_value(wast.iter().any(|s| s == "multi-value"))
         .strategy(strategy)?
-        .flags(settings::Flags::new(flag_builder));
+        .cranelift_debug_verifier(true);
     let store = HostRef::new(Store::new(&Engine::new(&cfg)));
     let mut wast_context = WastContext::new(store);
     wast_context.register_spectest()?;